the natural color is olive-brown dorsally to bronze-gold laterally and yellowish-white ventrally; black, gold, bronze, orange, red, pink, and white or combinations of these colors are often found; goldfish resemble common carp but lack barbels on upper jaw
widely distributed in Iowa waters, the origin of most of these specimens is from aquariums or bait buckets
zooplankton and aquatic larval insects
Goldfish is an exotic species that is widely distributed in Iowa waters. The origin of most of these specimen is from aquarium or bait buckets. Wild populations of goldfish have been reported in the Mississippi, Missouri, Des Moines, Iowa, Cedar and Wapsipinicon rivers. Several man-made recreational lakes, river impoundments, and surface mine lakes also have reproducing goldfish populations. They do not appear to jeopardize the integrity of native fishes and seldom spread far.
Goldfish have many unusual body forms and occur in a variety of colors. Bulge-eyed and multiple tailed forms are commonly produced for aquarium display, but normal body form is robust and laterally compressed. The natural color is olive-brown dorsally to bronze-gold laterally and yellowish-white ventrally. Black, gold, bronze, orange, red, pink, and white, or combinations of these colors are often found. Serrated spinous rays occur at the front of the dorsal and anal fins, which distinguishes goldfish from the native minnows.
Superficially, goldfish resemble common carp, but several features separate them. Goldfish lack barbels on the upper jaw, and the thin-lipped mouth is terminal. Body scales on goldfish do not have the dark spot, and no cross hatching pattern is present. Internally, the pharyngeal teeth of goldfish are arranged along a single row in 4-4 sequence, and they have heavy arches with the crowns at an angle.
The complete lateral line contains from 25 to 30 scales. The dorsal fin, which is much longer than those of native minnows, has from 15 to 19 soft rays, while the pectoral fins have from 15 to 17 soft rays, and the pelvic fins usually have 9 soft rays. Hybridization with common carp is known where both species inhabit the same waters.
Goldfish prefer sluggish or standing water with abundant aquatic vegetation. They are fairly specific in habitat selection, which probably accounts for their rather limited range. In addition, cultured goldfish are easy prey for predators because of their showy colors and domesticated nature. Spawning takes place from April through August as the female scatters adhesive eggs in shallow, vegetated water at random. Large female goldfish produce over 200,000 eggs.
This fish feeds on zooplankton and aquatic larval insects. In Iowa, adult fish typically range from 8 to 16 inches in length and weigh up to 2 pounds. This species is used extensively as bioassay animals for scientific purposes and has widespread use because it is hardy and easily kept in confinement. Iowa law prohibits release of goldfish into public water, however goldfish can be used as bait (placed on a hook while fishing).